Electrodynamic receiver



lli l i veniors Edwin SPridfiam M n l PeterlZJZmsen 4 1 i l lii PatentedApr. 6, 1926..

UNITED STATES ATENT OFFICE.

EDWIN S. PRIDHAM AND PETER L. JENSEN, OF OAKLAND, CALIFORNIA, ASSIGNORSTO THE MAGNAVOX COMPANY, OF OAKLAND, CALIFORNIA, A CORPORATION OFARIZONA.

ELECTRODYNAMIC RECEIVER.

- To all whom it may concern:

Be it known that we. EDWIN S. PRmHAM and Pnnnz L. J ENsnN, citizens ofthe United States, residing at Oakland, county of Alameda, and State ofCalifornia, have invented new and useful Improvements in ElectrodynamicReceivers, of which the following is a specification.

This invention relates to the manufacture and assembly ofelectro-dynamic receivers.

The type of receiver under consideration is shown, for instance, in ourapplication Serial No. 377,354, filed in the United States Patent OfficeApril 28th, 1920, and is characterized by the use of an annular coilrigidly connected to a diaphragm and disposed concentrically withrelation to an axial and a circumferential pole piece so as i to befreely movabie in a strong magnetic field.

The object of this invention. is to faci1itate the manufacture andassembly of a receiver of this type whereby to insure in a simple andready manner the correct positioning of the movable coil.

Referring to the accompanying drawing- Fig. 1 shows a side elevation,partly in section, of a receiver embodying our invention.

Fig. 2 shows a diagrammatic view of the enclosing casing andcircumferential pole piece, the fatter forming a cover for the casing.

Fig. 3 shows a diagrammatic view in section of the circumferential polepiece and base plate of the sound box in position upon a flanged gaugewhereby tocorrectly position these parts in assembling.

Fig. 4 shows a sectional View of the circumferential pole piece anddiaphragm illustrating the manner of positioning the movable coilconcentrically within the circumferential pole piece.

The device includes a receiver head assembly and an electro-magneticstructure. The receiver head assembly consists of a sound box A, amovable coil B and a circumferential pole piece C adapted to be placedupon the magnetic structure, The electromagnetic structure consists ofan iron cylinder D containing a magnetic coil E wound upon a core F,which forms one of the pole pieces.

In the manufacture and assembly of these parts it is of the greatestimportance that the coil B be correctly centered with relation to thepee pieces C and F. In other words, thi"s movable coil must be exactlyconcentric therewith and equally spaced therefrom. To bring this aboutin a simple and ready manner we first gauge thecylinder and then placethe core F therein and center it by means of a spacing disc 10 ofinsulating material. The circumferential polepiece C, which forms thecover for the cylinder, is provided with a shoulder or'reccss 11 whichis gauged to fit the cylinder D and acentral opening 12 is cut thereinso that it is exactly concentric with the core F, leavinga. trueconcentric space between. The sound box is next assembled upon thecircumferential pole piece. It will be noted that the sound boxcomprises a base plate 13, a diaphragm 14 and a top portion 15. The baseplate has a central aperture 16 and the correct position of the baseplate upon the circumferential pole piece is obtained by means of aflanged gauge 17. This gauge has a stem 18 to exactly fit the centralopening in the circumferential pole piece and a flange 19 to fit theopening in the base plate. hen the base plate is thus positioned, isattached to the pole piece by means of screws 20.

Next the coil B is put in position on the connected pole piece and baseplate. Previously the coil is attached to the diaphragm 14 by brackets21. A cylindrical gauge 29, having walls of a thinness corresponding tothe required space between the circumferential pole piece and coil ispositioned in the central opening in the circumferential pole piece andthe coil is then inserted in the cylindrical gauge, thereby insuringcorrect positioning of the coil. Thereafter the diaphragm is attached tothe base plate and the two pole pieces having been properly gauged, it.is assured that the coil will occupy a true concentric position equallyspaced from each of the pole pieces when the receiver head assembly isplaced upon the magnetic structure.

Having thus described our invention, what we claim and desire to secureby Lotters Patent is:

1. In the manufacture of an electro-dynamic receiver of the type havinga cylindrical casing containing an axial pole piece with i centering theaxial a circumferential pole piece surrounding the axial pole piece anda movable coil carried upon the diaphragm of a sound box disposedconcentrically between the pole pieces the steps of centering the axialpole piece within the" casing by means of a spacing ring titted againstthe axial polepiece and the casing above the coil surrounding the said:

axial po piece, gauging the circumferential pole piece to fit thecylindrical casing,

forming a circular aperture at the center ofthe circumferential polepiece and setting the movable coil in place within said capertiire bymeans of a cylindrical gauge removably placed between the coil and thewalls of the circumferential pole piece. 7

2. In the manufacture of an electro-dynamic receiver having acylindrical casing containing an axial pole piece with a circumferentialpole piece surrounding the axial pole piece and a movable coil carriedupon the diaphragm of a sound box disposed between the two pole pieces,the steps of recessing the circumferential pole piece to fit thecylindrical easing, providing the circumferential pole piece with acircular aperture centered with respect to the recess thereon,

pole piece within the eylindrical casing by means of'a spacing ringfitted against the axial pole'piece and the casing above the coilsurrounding the said axial pole piece and positioning the movable coilby means of a cylindrical gauge removably fitted within the circularaperture in the circumferential pole piece.

3. In the manufacture of an electro-dynamic receiver having acylindrical casing containing an axial pole piece with a circumferentialpole piece surrounding the axial polepiece and a movable coil carriedupon the diaphragm of a sound box disposed between the two pole pieces,the steps of recessing the circumferential pole pieces to fit thecylindrical casing and providing said pole piece with a circularaperture centered with respect to the recess centering the axial polepiece within thocylinder by means of a spacing ring, positioning theframe of the sound box upon the circumferential pole piece by means of aflanged gauge and thereafter positioning the movable coil with itsconnected diaphragm by means of a cylindrical gauge fitted within thecentral opening-in the circumferential pole piece.

4. An article Gf manufacture comprising an electromagnetic structureincluding a cylinder, an axial pole piece within the cylinder, amagnetic coil wound upon the pole piece and seated upon the bottom ofthe easing, a receiver head assembly detachably fitted upon saidcylinder and comprising a circumferential pole piece forming a coverplate for the cylinder. a sound box mounted upon the circumferentialpole piece, a movable eoil fixed to the diaphragm of the sound box andarranged concentrically between the two pole pieces, and a spacing dis:arranged between the axial pole piece and the cylinder and located abovethe magnetic coil to position said pole piece concentrically therewith.

EDWIN s. PRIDHAM. PETER L. JENSEN.

